This invention relates to the manufacturing and assembly of movable sockets, for example, ball joints as used in automotive steering and suspension systems, and more particularly, to a method and device for closing one end of a movable socket without spinning, swaging, or welding, by means of an expanding cover-plate. While the invention is described in detail with respect to automotive applications, those skilled in the art will recognized the broader applicability of the invention.
Conventional ball joints, and other movable sockets are used, for example, in automotive steering and suspension applications. The sockets comprise a housing having a circular cylindrical internal surface, a ball stud with a ball head contained in the housing, and a synthetic resin or sintered alloy bearing member supporting the ball head within the housing. These components are installed into the housing through a posterior opening, with the ball stud extending outward through an axially disposed anterior opening of a smaller diameter than the ball head. Traditionally, the posterior opening is closed by means of a cover-plate, spun, swaged, or welded in place. Once secured in place, the cover-plate presses on the bearing member either directly or indirectly through a resilient rubber intermediate component.
Bearing components within the housing, against which the ball head or moveable component is articulated, perform best when the housing material is fully hardened, as it is better able to withstand the stresses and frictional wear associated with movement of the bearing components. Accordingly, the use of hardened materials greatly extends the useful life of the bearing components and the housing. However, hardened material surfaces greatly hinder traditional spinning, sagging, or welding operations required to enclose the housing. Therefore, specialized heat treatment operations such as induction draw operations, or a reduction in the allowable hardness levels of the housing and bearing material surfaces must be employed when using traditional assembly methods. These options are utilized to prevent the housing from cracking during swaging or spinning operations. Welding is an alternative to swaging or spinning operations for securing the cover to the housing. However, welding hardened materials is a difficult and costly operation, and not commonly employed.
Accordingly, it is highly advantageous to develop an assembly method and associated components capable of enclosing a fully hardened housing without the need for specialized spinning, swaging, or welding operations.